1. Field of the Invention
The present invention relates to a mounting machine for semiconductor chips or the like. More particularly, the present invention relates to a method and apparatus for detaching a work piece having a small thickness, such as a semiconductor chip or the like, that has been diced and attached on an adhesive sheet from the adhesive sheet, and a mounting machine for mounting it on a printed circuit board or the like.
2. Related Background Art
Upon mounting semiconductor chips or the like, a pickup apparatus for transferring a plurality of work pieces such as semiconductor chips that have been separated by a dicing process on an adhesive sheet and picking up an adhering work piece has been conventionally used.
FIG. 11 is a front view showing an prior art chip pickup apparatus. The pickup apparatus 101 is composed of a suction collet 107 disposed above an adhesive sheet 111 on which work pieces 109 are attached and a push-up mechanism 113 disposed below the adhesive sheet 111. The push-up mechanism 113 is provided with a push-up pin holder 114 that can be moved up and down (in the Z direction indicated by a double-sided arrow). One end portion of the push-up pin holder 114 is connected with a driving mechanism and the other end portion is connected with a push-up pin 115. The push-up pin 115 is moved up and down by up and down movement of the push-up pin holder 114 caused by the driving mechanism.
In the above structure, the suction collet 107 is moved to a position at which it is in contact with the upper surface of a work piece 109 to be picked up. Then, the push-up pin 115 is moved upward by the push-up mechanism 113 so that the push-up pin 115 will be brought into contact with the lower surface of the work piece 109. After that, the work piece 109 is sucked by the suction collet 107.
Then, the push-up pin 115 and the suction collet 107 are moved upward at the same speed simultaneously (in the Z direction indicated by the double-sided arrow) in synchronization with each other while controlled by a control circuit, so that the work piece 109 is picked up while being held between the push-up pin 115 and the suction collet 107 (see, for example, paragraphs [0012] to [0013] or FIGS. 1 to 3 of Japanese Patent Application Laid-Open No. 2001-176891).
The above-described prior art apparatus has only one push-up pin, and there is the risk that a work piece 109 can be chipped or broken due to concentration of load exerted on the work piece 109. In view of this, a different prior art apparatus has a push-up member composed of a plurality of pins (see, for example, paragraphs [0013] to [0014], [0068] to [0069] or FIGS. 3 to 4 of Japanese Patent Application Laid-Open No. 2002-50670).
As described above, the prior art pickup apparatus is constructed in such a way that a work piece attached on the adhesive sheet is held between the cooperating push-up pin and the suction collet and detached from the adhesive sheet by upward movement of the pin and the collet. In this structure, if there is a difference in timing of the movement between the pin and the collet, an excessive load is applied to the work piece and the work piece can be chipped or broken. In addition, it is necessary in this prior art apparatus that the operation of the suction collet and the operation of the push-up pin be synchronized. Therefore, the structure of the pickup apparatus is generally complicated.